Hardened inserts for drill bits



June 18, 1968 J. w. FITTINGER 3,388,757

HARDENED INSERTS FOR DRILL BITS Filed March 23, 1967 Jdff/ W [/777/14656 INVENTOR.

United States Patent 3,388,757 HARDENED INSERTS FOR DRILL BITS Joseph W. Fittinger, Redondo Beach, Calif., assignor to Smith Industries International, Inc., Compton, Calif., a corporation of California Filed Mar. 23, 1967, Ser. No. 625,397 8 Claims. (Cl. 175-410) ABSTRACT OF THE DISCLOSURE Disclosure This invention relates to rock cutting bits, and more particularly to plug-like inserts therefor which are designed to give maximum penetration in rock, combined with maximum strength and wear qualities.

Previously, rock bit inserts in the form of plugs or teeth have been utilized which had a single transverse rib or crest having a cutting edge along each outer side edge thereof. If the convergent side edges of this single transverse crest were placed at too sharp an angle to each other, the tooth would break ofi or quickly wear. If the angle between the side faces of the crest was made greater, satisfactory penetration of the rock could not be secured.

Generally it is an object of the present invention to provide a tooth or insert for rock cutting bits having a plurality of crests convergent toward the tip of the tooth, and defined by relieved portions between the crests at the axially inner ends thereof to provide greatly improved penetration characteristics combined with maximum strength and wearing qualities.

The above and other objects of the invention will more fully appear from the following detailed description in connection with the accompanying drawing:

FIG. 1 is a sectional detail through a portion of a bit body with a bit tooth inserted therein;

FIG. 2 is an enlarged outer end view of the tooth of FIG. 1;

FIG. 3 is a perspective view thereof;

FIG. 4 is an outer end view of another form of tooth;

FIG. 5 is a perspective view of the tooth of FIG. 4;

FIG. 6 is a sectional detail taken approximately on the line 6-6 of FIG. 4.

A portion of a bit body 8 is shown in FIG. 1 and may be of any conventional type known in the art. It is shown provided with a socket 10 to receive an inserted tooth 12. The number and placement of the sockets and teeth 12 can vary depending upon the size of the bit and the hardness of the rock in which the bit is working. The tooth 12 is in the form of a plug which may be tightly secured in the socket 10 in any suitable manner. Preferably, it is cylindrical in cross section throughout a major portion of its length and an intermediate part thereof, defined by an edge or line 14- is defined as the base of a working portion of the tooth.

Converging outwardly, or toward the tip 16 of the tooth, are spaced relieved portions 18 which preferably are fiat, although they may be somewhat concave if desired. Alternating with the spaced relieved portions 18 are intermediate smaller relieved portions 20' which,

3,388,757 Patented June 18, 1968 while somewhat convergent toward the tip 16, are at a lesser angle to the longitudinal axis of the tooth 12 than are the spaced relieved portions 18. Between the spaced relieved portions 18 are crests 22 which converge and merge at the tip 16. These crests 22 have divergent axially inner ends 24 which define the axially outer limits of the intermediate relieved portions 20 and also define the edges 26 of said spaced relieved portions, the edges 26 comprising cutting edges. Additional cutting edges 28 are provided Where the curved sides of the intermediate re lieved portions 20 meet the curved basis of the spaced relieved portions 18. The crests 22 are somewhat arcuate transversely. These arcs may be compared with the arc of the tip as illustrated in FIGS. 1 and 3. Four such crests are illustrated in FIGS. 1 through 3.

It will be seen from the drawing that the angles between the spaced relieved portions 18 and the crests 22 are not sharp, and likewise the angles between the spaced relieved portions 18 and the intermediate relieved portions 20, as well as the angles between the intermediate relieved portions 20 and the crests 22, are rather wide so that the working portion of the tooth 12 has a bulk and strength characterized by the absence of thinner and less strong chisel-like edges. The construction provides maximum penetration qualities with strength and long wear characteristics.

In FIGS. 4 through 6 there is shown another form of tooth 30 having spaced relieved portions 32 intermediate relieved portions 34 and three convergent crests 36 instead of four crests shown in FIGS. 1 through 3. These relieved portions and crests bear a similar relationship to each other and those in the first form described, except of course that the angle between crests is greater than the angle between the first described crests 22. The crests 36 illustrated are shown to be wider transversely than the crests 22. These areas can be varied to suit different conditions of hardness of the rock being drilled but it is preferred that the crests have a minimal area commensurate with adequate strength and bearing surface to provide reasonable tooth life.

The three crested tooth of FIGS. 4 through 6, because it is wider, makes a sharper angle with the spaced relieved surfaces 32 and consequently, its penetration characteristics are greater than that of the four crested tooth of FIGS. 1 through 3. However, the four crested tooth, having more cutting edges, is more efficient in drilling softer formations. In hard granite however, the three crested tooth with its sharper angularity between the crests 36 and the spaced relieved portions 32 has greater penetration characteristics.

It should of course be understood that various changes can be made in the form and details of the structures without departing from the spirit of the invention.

I claim:

1. A hardened rock drill bit insert in the form of a tooth adapted to be firmly implanted in a socket in the bit with a working outer end projecting therefrom and terminating in a tip; wherein the improvement comprises a plug having a longitudinal axis and a longitudinally intermediate portion defining a base, the working end of said plug having spaced relieved portions thereabout convergent from said base toward the tip of said working end, intermediate relieved portions between the spaced relieved portions at a lesser angle to the longitudinal axis of the plug than said spaced relieved portions and of less extent axially of the plug than the spaced relieved portions, and non-aligned crests between said spaced relieved portions converging from said intermediate relieved portions and merging at said tip.

2. The structure in claim 1 and said crests being at an angle to the longitudinal surfaces of the longitudinally intermediate portions of the plug greater than those of said spaced relieved portions.

3. The structure in claim 1, and said crests being transversely arcuate.

4. The structure in claim 1, and said crests having side edges defining convergent side edges of said spaced relieved portions.

5. The structure in claim 1, and said crests having side edges defining side edges of said spaced relieved portions, and said side edges comprising cutting edges.

6. The structure in claim 1, and said crests having their divergent inner ends located axially outwardly from said base and defining the longitudinal outer limits of said intermediate relieved portions.

References Cited UNITED STATES PATENTS 5/1950 Ross 1754l0 X 7/1964 Dionisotti 175410 NILE C. BYERS, JR., Primary Examiner. 

